1. Field of the Invention
The present invention relates to unstacking apparatus, i.e., apparatus for removing articles from a stack. In particular, the present invention relates to apparatus for unstacking "cross-nested" articles, i.e., articles which are arranged such that each article in the stack is turned 90.degree. about the axis of the stack with respect to adjacent articles.
2. Description of the Prior Art
Many types of unstacking devices are known. One such device, disclosed in U.S. Pat. No. Re. 31,858, comprises a pair of laterally spaced-apart endless chains having article carriers mounted therebetween for removing articles from the top of the stack and/or adding articles to the top of the stack. That apparatus is specifically arranged so that the articles are moved only translationally, the conveyor paths being designed so as to provide a transfer portion at the top of the stack wherein the carriers and carried articles remain stationary for a time while the endless chain conveyors keep moving. But that unstacking device is designed for use with stacks in which all the articles are oriented in the same direction, the articles being removed from the stack one-at-time.
Unstackers are also known for unstacking cross-nested articles or groups of articles. A typical application is in unstacking courses of bricks in which alternate courses are oriented at right angles to each other. But these devices typically remove one layer of articles at a time and typically require either rotating the entire stack, or providing complicated transfer mechanism which rotates the layer after it is removed from the stack but before it is delivered to a discharge apparatus.